Shape each block of the finest walls to the irregular outline of the stones already laid, grinding the joints until they close without mortar; let the stones be as large and as many-sided as they come.
Lean the walls inward
Batter every wall a few degrees, thicker at the foot than at the top, and round its outer corners.
batter ≈ 3–5°
Inca walls lean inward on both faces, so that each wall is a slender trapezoid in section. In a region of frequent earthquakes the low centre of gravity and the inward lean help the walls to stand; the lean of the walls, the lean of the door jambs and the trapezoid of the niches are all one gesture. Buildings were roofed with steep timber-and-thatch roofs resting on the tops of the walls and gables.
Related rules
Give doors, windows and niches sides that lean inward, so that each opening is narrower at the top than at the bottom, and span it with a single stone lintel.
top width ≈ ⅘ of bottom width
For the most sacred buildings lay rectangular blocks in level courses that diminish in height towards the top of the wall, with pillowed faces and joints closed without mortar.
Cite this page Chris Paton, “Lean the walls inward”, The Textbook of Architecture, https://textbookofarchitecture.com/rule/inca-batter. Text, drawings and models licensed under CC BY-NC 4.0.